V6 cutting out (Page 1/1)
Lombok MAY 05, 01:55 AM
Hello forum. I am a long way away in Western Australia.and need some help. I have a 1987 V6 GT auto. Engine out and back in over about 6 months and now will start and run but as soon as I put it into gear it cuts out Back in park or neutral it starts straight away. Idles a bit fast at around 1500 after warm up. I have replaced the idle air mixture valve with no change. The adjustment screw on the intake makes little difference. Regards. Terry Ings alias Lombok
olejoedad MAY 05, 06:26 AM
Define 'cuts out'.

Disconnect the plug going into the transmission case on the front side (window side) of the transmission and see if the problem disappears.
Patrick MAY 05, 10:59 AM

quote
Originally posted by Lombok:

Idles a bit fast at around 1500 after warm up.



That's probably due to a vacuum leak. Usual cause is a cracked EGR tube.


quote
Originally posted by Lombok:

The adjustment screw on the intake makes little difference.



That's not an idle adjustment screw on the throttle body. It's an adjustment for the throttle-plate stop which was set at the factory. There was originally a plug over the screw head so people wouldn't mess with it. It'll now need to be properly re-set.

[This message has been edited by Patrick (edited 05-05-2022).]

phonedawgz MAY 05, 06:15 PM
Check your fuel pressure.
Dennis LaGrua MAY 06, 01:19 PM
Lets summarize the possible causes:
Torque converter solenoid lock up. Its common. Try Joes solution
Vacuum leak- do the test
Fuel pressure -measure it
Possible ignition problem.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Skybax MAY 06, 03:39 PM

quote
Originally posted by Patrick:

That's not an idle adjustment screw on the throttle body. It's an adjustment for the throttle-plate stop which was set at the factory. There was originally a plug over the screw head so people wouldn't mess with it. It'll now need to be properly re-set.




Yep, here is a step-by-step walk-thru that I wrote 20 years ago on how to reset it...

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If everything is working properly, no exhaust leaks, no EGR leaks, and
the engine is properly tuned, you can go through the IAC system.

Idle is controled by the IAC valve (idle air control) via the computer and
is not adjustable.

You can go over the system if your not happy with where it is idleing.
Proper idle for the V6 is roughly 900 RPM.

The set screw in the throttle body is for minimum air flow through the
throttle plate which is often misunderstood as the idle screw. Any tweaking
of the throttle stop screw will give the ECM fits. The ECM wants to be in
control of the idle and is not happy when it can't control it. If the normal
learn limits of the ECM are exceeded, they will be reset to nominal, causing
an erratic idle.

The IAC and associated passages need to be clean to work right. Remove the
IAC carefully. You can clean it (the nipple) using carb cleaner and a small
brass brush or rag. At this time also clean the throttle palte. Once clean,
install the IAC back in the throttle body and reconnect the IAC wires.

For the ECM to properly control idle, the throttle stop screw must be set
for "minimum air". This is a process that sets the idle with the IAC fully
extended. To fully extend the IAC, jumper ALDL pins A and B together (just
like when you check codes) and turn the key on, but do not start the car.
With the key on, not running, and in diags mode, the ECM will keep trying to
fully extend the IAC. After 30 seconds or so, pull the IAC connector off the
IAC *before* doing anything else. This will capture the IAC fully extended.

Now pull out the jumper in the ALDL, and start the car. Typically the
"minimum air" idle speed is in the 500 RPM range. I find the car can bearly
run at 550. So as long as you can get it to idle on its own between 600 &
700 your good. Set the idle using the throttle stop screw. (The engine
should be fully warm to do this.) Now shut the engine off and reconnect the
IAC wires. The ECM does not know where the IAC present position is, so pull
the ECM fuse (or disconnect the battery) for 20-30 seconds. (This will cause
a complete ECM reset of all learned parameters, including the learned IAC
ones. Then reinstall the ECM fuse.

Turn the key on, wait 10 seconds or so, and turn the key back off. This will
now reset the IAC to a known key-off "park" position. Now start the car. The
engine should idle properly under control of the ECM. There are some learned
values, such as an IAC offset for A/C, etc that need to be learned, but this
will happen under normal driving conditions. I suggest driving the car right
away under all conditions. Stop & go, steady cruising over 45 mph, full
throttle, and so on. Pull over a few times and turn the car off, then
restart it. The IAC can only learn X amount of counts with each run
position. If everything else on the engine is in good condition and
operating properly it should be around 900 RPM after coming to a complete
stop with slight variations and improve over time.

---------------------------------------------------------------------------------------------------

But you have to fix your problem first before you can do that.

[This message has been edited by Skybax (edited 05-06-2022).]

olejoedad MAY 06, 03:42 PM
.

[This message has been edited by olejoedad (edited 05-06-2022).]